ci: faster git clone

For some reason, some jobs in .github/workflows/validate.yml
have "fetch-depth: 0" argument to actions/checkout, meaning
"all history for all branches and tags". Obviously this is
not needed here.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

.github/workflows/validate.yml

@@ -188,8 +188,6 @@ jobs:
     steps:
     - name: checkout
       uses: actions/checkout@v5
-      with:
-        fetch-depth: 0
     - name: install deps
       run: |
         sudo apt -qq update
@@ -206,8 +204,6 @@ jobs:
     steps:
     - name: checkout
       uses: actions/checkout@v5
-      with:
-        fetch-depth: 0
 
     - name: check CHANGELOG.md
       run: make verify-changelog
@@ -236,8 +232,6 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
     - uses: actions/checkout@v5
-      with:
-        fetch-depth: 0
     - name: install bashbrew
       env:
         BASEURL: https://github.com/docker-library/bashbrew/releases/download